binary compatibility query

[Carl Shapiro]

FreeBSD Hackers,

I have a general question about the compatibility of FreeBSD binaries
within major releases.  If I build a binary for a given release of
FreeBSD can I make a reasonable guarantee that the binary will run on
both previous and subsequent minor releases of the same major release?
In other words, if I build on FreeBSD 6.3 and do not rely on anything
unique to 6.3 (such as the presence of specific version strings) how
certain can I be that the code will or will not run on 6.2, 6.1 etc.?

Also, is this documented anywhere on the FreeBSD web site?  The
closest thing I could find is the following guidance for driver
vendors which falls just short of answering my question:

http://wiki.freebsd.org/VendorInformation

(Too bad the fancy illustration is missing.)

Regards,

Carl